The present invention relates to a display driver, an electro-optical device, and a method of driving an electro-optical device.
In an active matrix liquid crystal device (electro-optical device in a broad sense), the operation of writing data into a liquid crystal (electro-optical substance in a broad sense) layer in each pixel through switching elements connected with one scan line is performed by a dot sequential drive. A scan line of the liquid crystal device is sequentially selected by a scan driver, and a data line of a liquid crystal device is driven by a data driver (display driver) based on display data. The scan driver and the data driver are timing-controlled by a display controller.
There may be a case where display unevenness occurs due to bias of voltage applied to a liquid crystal. The liquid crystal deteriorates if the polarity of the voltage applied to the liquid crystal remains unchanged. In order to prevent occurrence of these problems, a polarity reversal drive is performed in which the polarity of the voltage applied to the liquid crystal is reversed at a given timing. In the polarity reversal drive, voltage is applied to one end of the liquid crystal so that the polarity is reversed with respect to the potential applied to the other end of the liquid crystal. The polarity means the polarity of the voltage applied between both ends of the liquid crystal. In the active matrix liquid crystal device using a thin-film transistor (TFT), potential applied to a common electrode which faces a pixel electrode through a liquid crystal is changed in order to perform the polarity reversal drive.
As the polarity reversal drive, a frame reversal drive in which the polarity is reversed in units of vertical scan periods, a line reversal drive in which the polarity is reversed in units of horizontal scan periods, a polarity reversal drive in which a dot reversal drive in which the polarity is reversed in each dot is combined with the line reversal drive, and the like have been proposed.
The polarity reversal drive is performed in synchronization with a polarity reversal signal. The polarity reversal signal is generated by the display controller. The display controller generates the polarity reversal signal together with a horizontal synchronization signal which specifies the horizontal scan period and a vertical synchronization signal which specifies the vertical scan period in order to control the display timing. The polarity reversal signal is generated by a circuit disclosed in Japanese Patent Application Laid-open No. 6-38149, for example.